1. Field of the Invention
The present invention relates generally to a chuck and a method for cooling a planar electronic substrate, such as a wafer comprised of a plurality of high powered semiconductor chips. More particularly, it relates to such a chuck and method in which the wafer is placed on the chuck and cooled by a combination of two ways: direct contact with flowing water or other coolant, and indirect cooling via conduction through a thin film of the coolant and into fin arrays in the chuck. Most especially, it relates to such a chuck and method in which the wafer is held onto the chuck by the liquid coolant, which is circulated at sub-atmospheric pressure.
2. Description of the Prior Art
Emitter coupled logic (ECL) integrated circuit chips dissipate substantial amounts of power. To enable testing (commonly called probing) ECL chips while still in wafer form, pulsed power testing is often used. The die site is probed, and power is supplied only for a fraction of a second. At 30 watts/cm.sup.2 power dissipation, which is typical for ECL, the temperature of an isolated die rises at 300.degree. C. per second. In reality, there is some heat sinking to adjacent silicon and to the wafer chuck of a probing station, so short tests can be run without burning up the chip.
Advanced ECL microprocessor chips now under development will have a much higher watt density of almost 100 watts/cm.sup.2. Such microprocessor chips also have a clocking scheme that would complicate designing the chip for pulsed power testing. Tester software for pulsed power testing is also more complicated than is the case with continuous testing. Thus, it is desired to run the chip continuously at full power during probing. This problem is not unique to such ECL microprocessor chips. Such a capability is desirable in almost any high powered wafer probing application.